Siloxane-unsaturated ester coated product

ABSTRACT

AN ARTICLE OF MANUFACTURE COMPRISING A SUBSTRATE AND AN ORGANIC COATING THEREON CROSSLINKED IN SITU BY IONIZING RADIATION AND, PRIOR TO CURING, CONSISTING ESSENTIALLY OF AN ALPHA-BETA OLEFINICALLY UNSATURATION SILOXANE. THE UNSATURATED SILOXANE IS PREPARED BY REACTING A HYDROXYALKYL ESTER OF AN ALPHA-BETA OLEFINICALLY UNSATURATED MONOCARBOXYLIC ACID WITH A SILOXANE HAVING AT LEAST TWO FUNCTIONAL GROUPS SELECTED FROM HYDROXYL GROUPS AND ALKOXY GROUPS. THE UNSATURATED SILOXANE CAN BE PREPARED BY A CONVENTIONAL CONDENSATION REACTION.

United States Patent 3,746,567 SILOXANE-UNSATURATED ESTER COATED PRODUCTJohn D. Nordstrom, Detroit, Mich., assignor to Ford Motor Company,Dearhorn, Mich.

No Drawing. Original application Nov. 18, 1968, Ser. No. 776,765.Divided and this application Dec. 17, 1970, Ser. No. 99,249

Int. Cl. 344d 1/50; B32b 15/08; C08f 35/02 US. Cl. 117-9331 8 ClaimsABSTRACT OF THE DISCLOSURE An article of manufacture comprising asubstrate and an organic coating thereon crosslinked in situ by ionizingradiation and, prior to curing, consisting essentially of an alpha-betaolefinically unsaturation siloxane. The unsaturated siloxane is preparedby reacting a hydroxyalkyl ester of an alpha-beta olefinicallyunsaturated monocarboxylic acid with a siloxane having at least twofunctional groups selected from hydroxyl groups and alkoxy groups. Theunsaturated siloxane can be prepared by a conventional condensationreaction.

This application is a division of application Ser. No. 776,765, filedNov. 18, 1968, now abandoned.

This invention relates to the art of coating and is concerned with paintand painted articles of manufacture wherein the painted surface has highresistance to weathering. This invention is particularly concerned witharticles of manufacture having external surfaces of wood, metal orpolymeric solid coated with an in situ formed polymerization product ofa film-forming, radiationcurable, paint binder crosslinked on suchsurface by ionizing radiation and comprising the reaction product of onemolar part siloxane having at least two hydroxyl and/or hydrocarbonoxygroups and, preferably at least two molar parts of, a hydroxyl bearingester of an alpha-beta unsaturated carboxylic acid.

In this application, the term paint is meant to include pigment and/orfinely ground filler, the binder without pigment and/or filler or havingvery little of the same, which can be tinted if desired. Thus, thebinder which is ultimately converted to a durable film resistant toWeathering, can be all or virtually all that is used to form the film,or it can be a vehicle for pigment and/or particulate filler material.

The siloxanes employed in the preparation of the binder have a reactivehydroxyl or hydrocarbonoxy group bonded to at least two of its siliconatoms. The term siloxane as employed herein refers to a compoundcontaining a linkage, with the remaining valences being satisfied by ahydrocarbon radical, a hydrocarbonoxy group, hydroxyl group, or anoxygen atom which interconnects the silicon atom providing such valencewith another silicon atom.

The acyclic siloxane molecules which can be used in preparing the paintbinder resins in this invention advantageously contain about 3 to about18 silicon atoms per molecule with corresponding oxygen linkages. Thepreferred siloxanes are represented by the following general formula:

X X X wherein n is at least 1 and X is (a) a C to C monovalenthydrocarbon radical, preferably a C to 4 alkyl radical,

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or (b) C to C monovalent hydrocarbonoxy radical, preferably a C to Calkoxy radical, or (c) a hydroxyl radical, or (d) hydrogen, with atleast two of the X groups separated by a linkage being either (b) or(c).

The cyclic siloxanes which can be used in preparing the paint binderresins of this invention contain at least 3, preferably 6 to 12, andordinarily not more than 18, silicon atoms per molecule withcorresponding oxygen linkages. The cyclic polysiloxanes used may takethe form of one of the following type formulas:

(I) n n n" where n=an odd numbered positive integer of at least 3,n'=2n, and

X=(a) a C to C monovalent hydrocarbon radical,

preferably a C to C alkyl radical, or (b) a C to C monovalenthydrocarbonoxy radical,

preferably a C to C alkoxy radical, or (c) a hydroxyl radical, or (d)hydrogen-with at least two of the X groups separated by a linkage beingeither (b) or (c) Exemplified by the following formula:

n1=an odd numbered positive integer of at least 5, n"=n+3, and "l=6, 6+3or 6+ a multiple of 3 X-=(a) a C to C monovalent hydrocarbon radical,preferably a C to C alkyl radical, or (b) a C to C monovalenthydrocarbonoxy radical.

preferably a C to C alkoxy radical, or (c) a hydroxyl radical, or (d)hydrogen-with at least two of the X groups separated by a linkage beingeither (b) or (c) Exemplified by the following structural formula:

x x XS'i-O-Si X X (III) X Si O H where n-=6 or a multiple of 6, l n': 8,8+6, or 8+ a multiple of 6 n" =8, 8+9, or 8+ a multiple of 9 X= (a) a Cto C monovalent hydrocarbon radical, prcf- Exemplified by the followingstructural formula:

erably a C to C alkyl radical, or

(b) a C to C monovalent hydrocarbonoxy radical, x x preferably a C to0,, alkoxy radical, or ii x O-i (c) a hydroxyl radical, or X X (d)hydrogen-with at least two of the X groups l separated by a A g X 0\ 0'1- /O X xli---oi-x x m 10 x X linkage being either (b) or (c) where mis a positive integer. Exemplified by the following structural formula:A variety of methods are known to the art for prepap ing siloxanes.These include controlled hydrolysis of X silanes, polymerization of alower molecular weight silox- -0 ane, reacting silicon tetrachloridewith an alcohol, etc. x o 0 x The preparation of siloxanes and theirincorporation into organic resins is disclosed in US. Pats. 3,154,597;3,074,- 904; 3,044,980; 3,044,979; 3,015,637; 2,996,479; 2,973,- 0 x287; 2,937,230; and 2,909,549. The hydroxyl bearing ester is preferablya monohydroxy alkyl ester of an alpha-beta olefinically unsaturatedmonocarboxylic acid. The preferred hydroxy esters are acrylates andmethacrylates in that they provide olefinic unsaturation between theterminal carbon atoms and are readily polymerizable at relatively lowdoses of ionizing or a condensation dimer, trimer, etc., thereof formedwith loss of water or alcohol radiation. A partial and exemplary list ofsuch acrylates (IV) n' n n" follows: where 2-hydroxyethyl acrylate ormethacrylate 3O n=an even numbered positive integer of at least 4,2-hydroxypropyl acrylate or methacrylate n'=n+4, and 2-hydroxybutylacrylate or methacrylate n" =4, 4+3, or 4+ a multiple of 3Z-hydroxyoctyl acrylate or methacrylate X: (a) a C to C monovalenthydrocarbon radical, pref- 2-hydroxydodecanyl acrylate or methacrylateerably a C to C alkyl radical, or 2-hydroxy-3-chloropropyl acrylate ormethacrylate (b) a C to C monovalent hydrocarbonoxy radical,2-hydroxy-3-acryloxypropyl acrylate or methacrylate preferably a C to Calkoxy radical, or 2-hydroxy-3-inethacryloxypropyl acrylate or methacry-(c) a hydroxyl radical, or late (d) hydrogen-with at least two of the Xgroups Z-hydroxy-3-allyloxypropyl acrylate or methacrylate separated bya 40 2-hydroxy-3-cinnamylpropyl acrylate or methacrylate I I2-hydroxy-3-phenoxypropyl acrylate or methacrylate XSiOSi-X2-hydroxy-3-(o-chlorophenoxy)propyl acrylate or meth- I acrylate2-hydroxy-3-(p-chlorophen0xy)propyl acrylate or linkage being either (b)or (c) 2 g y g di m h Exemplified by the following structural formula: gg gigg c Drop enoxwpropyl acrylate or 2-hydroxy-3-acetoxypropyl acrylateor methacrylate X X x 2-hydroxy-3-propionoxypropyl acrylate ormethacrylate g g 2-lliggroxy-3-chloroacetoxypropyl acrylate or methacry-I I 2-hydroxy-3-dichloroacetoxypropyl acrylate or methx-si --O-Si O-Si-Xacrylate I I I 2-hydroxy-3-trichloroacetoxypropyl acrylate or methracrylate 2-hydroxy-3-benzoxypropy1 acrylate or mcthacrylate where m is oor a positive integer 2-liycrl3rliirty-3-(o-chlorobenzoxy)propylacrylate or methn n n" 2-hydroxy-3-(p-chlorobenzoxy)propyl acrylate ormethwhere acrylate 2-h drox -3- 2,4-dichlorob n x o l l t n=an evennumbered positive integer of at least 8, z g e Z0 y)pr py acry a e orand 2-h drox -3- 3 4-dichlorobenzox ro lacr l t o n"=11, n+3, or 11+amultiple of s g fl M W y a e r a C1 to a monovfllem hydrocarbon adlcal,P 2-hydroxy-3-(2,4,6-trichlorophenoxy)propyl acrylate or erably a C to Calkyl radical, or methacrylate a 1 to a monovalfint hydrocflrbonoxyfadlcal, 2-hydroxy-3-(2,4,5-trichlorophenoxy)propyl acrylate orpreferably a C to 0, alkoxy radical, or methacrylate a y y radical, 2-hdroxy-3- o-chloro henox acetox ro l acr late (d) hydrogen-with at leasttwo of the X groups methacsylate p y py y Separated y a2-hydroxy-3-phenoxyacetoxypropyl acrylate or meth- J E! acrylate X- li0-l-X 2-hydroxy-3-(p-chlorophenoxyacetoxy)propyl acrylate or methacrylate2-liydroxy-3-(2,4-dichlorophe o acetoxy)propyl acrylinkage being either13) or (c) WA late 01 methacrylate xy w 2-hydroxy-3-(2,4,S-trichlorophenoxyacetoxy)propyl acrylate or methacrylate2-hydroxy-3-crotonoxypropyl acrylate or methacrylate2-hydroxy-3-cinnamyloxypropyl acrylate or methacrylate3-acryloxy-2-hydroxypropyl acrylate or methacrylate3-allyloxy2-hydroxypropyl acrylate or methacrylate3-chloro-2-hydroxypropyl acrylate or methacrylate3-crotonoxy-2-hydroxypropyl acrylate or methacrylate In addition toacrylates and methacrylates one may also use cinnamates, crotonates,etc.

The term ionizing radiation as employed herein means radiation havingsuflicient energy to eifect polymerization of the paint films hereindisclosed, i.e. energy equivalent to that of about 5,000 electron voltsor greater. The preferred method of curing films of the instant paintsupon substrates to which they have been applied is by subjecting suchfilms to a beam of polymerization effecting electrons having an averageenergy in the range of about 100,000 to about 500,000 electron volts.When using such a beam, it is preferred to employ a minimum of 25,000electron volts per inch of distance between the radiation emitter andthe workpiece where the intervening space is occupied by air. Adjustmentcan be made for the relative resistance of the intervening gas which ispreferably an oxygen-free inert gas such as nitrogen or helium. I preferto employ an electron beam which at its source of emission has averageenergy in the range of about 150,000 to about 500,000 electron volts.

The films formed from the paints of this invention are advantageouslycured at relatively low temperatures, e.g. between room temperature (20to 25 C.) and the temperature at which significant vaporization of itsmost volatile component is initiated, ordinarily between 20 and 70 C.The radiation energy is applied at dose rates of about 0.1 to about 100mrad per second upon a preferably moving workpiece with the coatingreceiving a total dose in the range of about 0.5 to about 100,ordinarily between about 1 and about 25, and most commonly between 5 and15 mrad. The films can be converted by the electron beam intotenaciously bound, wear and weather resistant, coatings.

The abbreviation mrad as employed herein means 1,000,000 rad. The termrad as employed herein means that dose of radiation which results in theabsorption of 100 ergs of energy per gram of absorber, e.g. coatingfilm. The electron emitting means may be a linear electron acceleratorcapable of producing a direct current potential in the rangehereinbefore set forth. In such a device electrons are ordinarilyemitted from a hot filament and accelerated through a uniform voltagegradient. The electron beam, which may be about A; inch in diameter atthis point, is then scanned to make a fanshaped beam and then passedthrough a metal window, e.g. a magnesium-thorium alloy, aluminum, analloy of aluminum and a minor amount of copper, etc., of about 0.003inch thickness.

The film-forming material should have an application viscosity lowenough to permit rapid application to the substrate in substantiallyeven depth and high enough so that at least a 1 mil (.001 inch) filmwill hold upon a vertical surface without sagging. Such films willordinarily be applied to an average depth of about 0.1 to about 4 milswith appropriate adjustment in viscosity and application technique. Itwill be obvious to those skilled in the art that the choice of siloxaneand of hydroxy esters in preparing this coating can be varied so as tovary the viscosity of the resultant product. Many of these products havea suitable viscosity for application by conventional paint applicationtechniques, e.g. spraying, roll coating, etc., without addition ofdiluents. When needed, the siloxane-unsaturated ester product may beemployed in combination with vinyl monomers, allylic compounds,unsaturated resins or in solution with nonpolymerizable, volatilesolvents, e.g. toluene, Xylene, etc., which can be flashed ofi afterapplication. This invention is particularly concerned with thosecoatings wherein the film-forming solution consists essentially of thesiloxaneunsaturated ester, herein defined to mean coatings wherein saidsiloxane-unsaturated ester product constitutes at least about weightpercent of the film-forming binder.

The term vinyl monomers as used herein refers to a monomeric compoundhaving a terminal group and exclude allylic compounds. The preferredvinyl monomers are esters of C to C monohydric alcohols and acrylic ormethacrylic acid, e.g. ethyl acrylate, ethyl methacrylate, butylacrylate, butyl methac-' rylate, octyl acrylate, Z-ethyl hexyl acrylate,etc. Alcohols of higher carbon number, e.g. C -C can also be used toprepare such acrylates and methacrylates. Vinvl hydrocarbon monomers,e.g. styrene and alkylated styrenes such as vinyl toluene, alpha-methylstyrene, etc., may be used separately or in combination with acrylatesand methacrylates. Also in combination with acrylates and methacrylatesand/or vinyl hydrocarbon monomers, there may be used minor amounts ofother vinyl monomers such as nitriles, e.g. acrylonitrile, acrylamide,N-methylol acrylonitrile, vinyl halides, e.g. vinyl chloride, and vinylcarboxylates, e.g. vinyl acetate.

When the siloxane-unsaturated ester product is employed as the solepolymerizable component of the paint application, it may be applied withor without pigment and depending upon its own viscosity with or withoutnnnpolymerizable solvent.

This invention will be more fully understood from th followingillustrative examples:

EXAMPLE 1 A siloxane-unsaturated ester coating material is prepared fromthe following components in the manner hereinafter set forth.

1 A commercially available methoxylated partial hydrolysate ofmonophenyl and phenylmethyl silanes (largely condenseddimethyltriphenyltrimethoxytrisiloxane) and has the following typicalproperties Average molecular weight 750-850 Average number of siliconatoms per molecule 5-6 Average number of methoxy groups per molecule 3-4The siloxane, the methacrylate monomer and hydroquinone polymerizationinhibitor are heated to C. in a flask fitted with a Barrett typedistillation receiver. The titanate catalyst is added and the.temperature is raised to C. over a three hour period during which timemethanol is removed by distillation. The cooled reaction product has aviscosity of 0.6 stoke at 25 C. This material is applied as a 0.7 milfilm upon metal and wood substrates and homopolymerized thereon byionizing radiation in the form of an electron beam. The conditions ofirradiation are as follows:

Average beam potential 275 =kv.

Average current 25 milliamperes.

Atmosphere Nitrogen.

Distance, emitter to workpiece winches.

Total dose 15-20 mrad.

EXAMPLE 2 The procedure of Example 1 is repeated except that thepolysiloxane is a methoxylated partial hydrolysate of monophenyl andphenylmethyl silanes consisting essential- 1y ofdimethyltriphenyltrimethoxytrisiloxane and has the following typicalproperties:

A siloxane-unsaturated ester coating material is prepared from thefollowing components in the manner hereinafter set forth.

Reactants: Parts by weight Hydroxy functional cyclic siloxane 1 200'Hydroxyethyl methacrylate 71 Hydroquinone 0.1 Xylene, solvent 116 1 Acommercially available hydroxy functional, cyclic, polysiloxane havingthe following typical properties Hydroxy content, Dean-Stark:

Percent condensible 5.5 Percent free 0.5 Average molecular weight 1600Combining weight 4 0 Refractii e Index 1,531 to 1,539 Softening% point,Durrans Mercury Method, de 200 grees At 60% solids in xylene Specificgravity at 77 F. 1.075 Viscosity at 77 F., centipoises A391)GardnerHoldt A three neck flask fitted with a stirring motor, athermometer, a nitrogen inlet and a Barrett trap is charged with thesiloxane, the methacrylate, the xylene and the hydroquinone. Thissolution is heated to reflux, 138 C., over a 30 minute period. Nitrogenis bubbled into the reaction throughout the whole procedure. By-productwater is slowl removed and the temperature gradually rises to 146 C.After hours,8.5 ml. of water is collected indicating nearly completereaction. The xylene is removed by reduced pressure distillation and theproduct is then diluted again with xylene to spraying consistency. Thissolution is applied to metal, wood and polymeric (ABSacrylonitrile-butadiene-styrene) substrates to an average depth of about1 mil and later cured thereon by an electron beam employing the sameconditions as in Example 1.

EXAMPLE 4 The procedures of Examples 1-3 are repeated except that anequivalent amount of Z-hydroxyethyl acrylate is substituted for thehydroxyethyl methacrylate.

EXAMPLE 5 The procedures of Examples 1-3 are repeated except that anequivalent amount of 2-hydroxypropyl methacrylate is substituted for thehydroxyethyl methacrylate.

EXAMPLE 6 The procedures of Examples 1-3 are repeated except that anequivalent amount of Z-hydroxybutyl acrylate is substituted for thehydroxyethyl methacrylate.

EXAMPLE 7 The procedures of Examples 1-3 are repeated except that anequivalent amount of Z-hydroxyoctyl acrylate is substituted for thehydroxyethyl methacrylate.

EXAMPLE 8 The procedures of Examples 1-3 are repeated except that anequivalent amount of 2-hydroxydodecanyl methacrylate is substituted forthe hydroxyethyl methacrylate.

EXAMPLE 9 The procedures of Examples 1-3 are repeated except that anequivalent amount of S-chloro-Z-hydroxypropyl acrylate is substitutedfor the hydroxyethyl methacrylate.

EXAMPLE 10 The procedures of Examples 1-3 are repeated except that anequivalent amount of 3-acryloxy-Z-hydroxypropyl methacrylate issubstituted for the hydroxyethyl methacrylate.

EXAMPLE 11 The procedures of Examples 1-3 are repeated except that anequivalent amount of 3-crotonoxy-2-hydroxypropyl acrylate is substitutedfor the hydroxyethyl methacrylate.

EXAMPLE 12 The procedures of Examples 1-3 are repeated except that anequivalent amount of 3-acryloxy-2-hydroxypropyl cinnamate is substitutedfor the hydroxyethyl methacrylate.

EXAMPLE 13 The procedures of Examples 1-3 are repeated except that anequivalent amount of 3-acryloxy-2-hydroxypropyl crotonate is substitutedfor the hydroxyethyl methacrylate.

EXAMPLE 14 The procedure of Example 1 is repeated except that thereactants are proportioned to provide in the reaction mix 412 parts byweight of the polysiloxane, 195 parts by weight of hydroxyethylmethacrylate and 0.2 part by Weight of hydroquinone.

EXAMPLE 15 The procedure of Example 1 is repeated except that thereactants are proportioned to provide in the reaction mix 206 parts byweight of the polysiloxane, 65 parts by weight of hydroxyethylmethacrylate and 0.1 part by weight of hydroquinone.

EXAMPLE 16 The procedure of Example 1 is repeated except that thepolysiloxane employed is dimethyltriphenyltrimethoxytrisiloxane.

EXAMPLE 17 The procedure of Example 1 is repeated except that thepolysiloxane employed is dipropoxytetramethylcyclotrisiloxane.

EXAMPLE 18 The procedure of Example 1 is repeated except that thepolysiloxane employed is dibutoxytetramethyldisiloxane.

EXAMPLE 19 The procedure of Example 1 is repeated except that thepolysiloxane employed is pentamethyltrimethoxytrisiloxane.

EXZAMPLE 20 A pigmented paint is prepared by premixing 75 parts byweight of the siloxane-unsaturated ester product of Example 3 with 150parts by weight of commercial grade titanium dioxide pigment and 20parts by weight of methyl methacrylate. The mixture is ground by shakingwith an equal weight of glass beads in a conventional paint shaker for30 minutes. The premix is diluted with an additional 75 parts by weightof the siloxane-unsaturated ester product. The paint is applied to analuminum panel by a draw down with a wire wound rod. The paint is curedwith 20-25 mrad dose of 275 kv., 25 ma. electron beam in a nitrogenatmosphere. The paint-film is 1.9 mils thick and has a gloss of 100 asmeasured by a Gardner 60 gloss meter. The panel is mounted in a twincarbon arc weatherometer. After 1,216 hours exposure, the paint has a 60gloss of and showed no chalk formation.

The weatherometer is an instrument used to obtain weathering data at anaccelerated rate. In this case, the light emitted by carbon arcs is usedto provide a high intensity source of ultraviolet and visible light.Water spray is allso applied to the coating during part of the exposureCyC e0 9 EXAMPLE 21 The procedure of Example 1 is repeated except thatcuring is effected with a beam potential of 175,000 volts with theworkpiece 3 inches from the emitter and at 400,- 000 volts at incheseach being in a nitrogen atmosphere containing minor amounts of carbondioxide.

It will be understood by those skilled in the art that modifications canbe made within the foregoing examples within the scope of the inventionas hereinafter claimed.

I claim:

1. An article of manufacture comprising in combination a substrate and acoating thereon comprising the polymerization product of a film-formingcoating material crosslinked in situ by ionizing radiation, said coatingmaterial on a pigment and mineral filler-free basis consisting of analpha-beta olefinically unsaturated siloxane formed by reacting at leasttwo molar parts of a monomeric monohydroxy alkyl ester of an alpha-betaolefinically unsaturated monocarboxylic acid with one molar part of a Si-Si siloxane having at least two functional groups selected from hydroxygroups and C -C alkoxy groups.

2. An article of manufacture in accordance with claim 1 wherein saidmonohydroxy alkyl ester is an acrylate or methacrylate.

3. An article of manufacture in accordance with claim 1 wherein saidsiloxane contains about 3 to about 12 silicon atoms per molecule.

4. An article of manufacture comprising in combination a substrate and apolymerized organic coating on a surface thereof having an average depthin the range of about 0.1 to about 4 mils and crosslinked in situ byionizing radiation, said coating on a pigment and particulatefiller-free basis consisting of an alpha-beta olefinically unsaturatedsiloxane formed by reacting at least two molar parts of a monomericmonohydroxy alkyl ester of acrylic or methacrylic acid with a Si -Sisiloxane having at least two functional groups selected from hydroxygroups and C -C alkoxy groups.

5. An article of manufacture comprising in combination a substrate and apolymerized organic coating on a surface thereof having an average depthin the range of about 0.1 to about 4 mils and crosslinked in situ byionizing radiation, said coating on a pigment and particulatefiller-free basis consisting of an alpha-beta olefinically unsaturatedsiloxane formed by reacting at least two molar parts of a monomericmonohydroxy alkyl ester of acrylic or methacrylic acid with a Si Sisiloxane wherein at least two silicon atoms thereof have one valencesatisfied by a functional group consisting of hydroxyl groups and C -Calkoxy groups, the remaining valences of the silicon atoms of saidsiloxane being satisfied by oxygen, hydrocarbon radical, hydrocarbonoxyradical, hydrogen or hydroxyl.

6. An article of manufacture in accordance with claim 5 wherein said C-C alkoxy groups are methoxy groups.

7. An article of manufacture in accordance with claim 5 wherein said C-C alkoxy groups are methoxy groups and said monohydroxyalkyl ester isan acrylate or methacrylate.

8. An article of manufacture in accordance with claim 5 wherein saidmonohydroxy alkyl ester is an acrylate or methacrylate.

References Cited UNITED STATES PATENTS 3,575,910 4/1971 Thomas 117-161ZA 3,437,512 4/1969 Burlant et a1. 117-9331 3,437,513 4/1969 Burlant eta1. 117-9331 3,577,263 5/1971 Nordstrom 117-9331 3,577,262 5/1971Nordstrom 117-9331 3,577,264 5/1971 Nordstrom 117-9331 3,585,065 6/1971Johnson 117-9331 3,644,566 2/ 1972 :Kincheloe et a1 260-827 WILLIAM D.MARTIN, Primary Examiner W. H. SCHMIDT, Assistant Examiner US. Cl. X.R.

ll7-l35.l, 138.8 UA, i148, DIG. 3; 204-159.15; 260-37 SB, 46.5 R, 46.5UA, 46.5 Y. 827

